Floatovoltaics Marches On

Every house in the village in which I reside is listed on the US National Register of Historic Places for “architectural significance.” After living in a 140-year-old home for eight years, I’ve found that one of the best things about having an old, historically unalterable dwelling is that it’s really easy to shut down pitches from SolarCity salespeople in certain big-box hardware stores. They ask “Why not residential solar?” and I respond “Because the government says I can’t put panels on my roof.” End of conversation.

But for those with suitable homes in sunny locales, covering their roofs with PV modules makes more sense. Rooftop solar is practical because solar installations are often hampered by space limitations. The growing trend of placing floating solar arrays on reservoirs and other bodies of water is emerging as a creative solution to this problem.

Floating solar, now sometimes known by the snappier “floatovoltaics,” has been in development for about a decade. It typically involves fitting PV modules to pontoons, stringing the pontoons together to form an array, and placing the whole thing on the surface of a lake, pond, canal, or reservoir. Floatovoltaic solar has a number of advantages over land-based plants. It has a smaller visual footprint, making for a more favorable argument against NIMBY opposition. The body of water cools the system, achieving higher efficiencies. Perhaps most importantly, floatovoltaic technology saves valuable land area that could be used for other purposes.

Small, experimental floatovoltaic systems have been springing up all over the globe since the first installation in California’s Wine Country began operation in 2008. Until recently, though, large-scale installations were pretty much nonexistent. Japan, a country recognized for its post-Fukushima renewables investment, announced earlier this year that the world’s largest floatovoltaic plant was under construction near Tokyo. The power station, consisting of 51,000 solar modules and covered 180,000 square meters of the surface of the Yamakura Dam reservoir, will generate 13.7 MW.

As floating solar becomes more common, it’s becoming clear that the technology has far-reaching environmental benefits beyond simply reducing the carbon footprint. Brazil, for example, has applied floatonics to salvage the remains of a decades-old engineering disaster. The controversial Balbina Hydroelectric Dam completed in the late 1980s involved flooding over 1,000 square miles of Amazon rainforest. The National Institute for Amazonian Research has referred to the massive reservoir as a “methane factory,” emitting more greenhouse gas than coal plants. For all the environmental damage, the project now produces only a fifth of its 250 MW capacity. Brazilian company Sunlution is now working in conjunction with French floating solar firm Ciel et Terre to install floating panels on the hydroelectric reservoir to revitalize the failed hydroelectric project and reduce the reservoir's environmental impact.

The western and southwestern US, where drought and evaporation plague lakes and other bodies of water, might be a future application for floatovoltaics. In addition to the advantages mentioned above, floating solar installations shield water surfaces from the hot sun, reducing evaporation and inhibiting algae growth in reservoirs. A recently published op-ed suggested that lakes Mead and Powell—two Colorado River reservoirs threatened by drought and overuse—might benefit from floatovoltaics, and extra electricity is never a bad thing.

Large-scale floating solar systems are still hampered by cost, and I’m sure a lot of local residents would rather not see their water features—man-made or not—covered with PV modules. But with a host of big commercial projects underway, it appears floating solar isn’t going away anytime soon.

Image credit: Thomas Roche / CC BY-SA 2.0